One example of this type of handwriting input device is an input device having a function of electronically or optically reading a letter and a figure written and drawn by a writing implement called a marker on a white sheet or a whiteboard (hereinafter, referred to as an electronic-blackboard-type handwriting input device), and the input device is widely used majorly in a meeting and a presentation. A reading system is: a board surface moving type that rotates the white sheet by a roller and a motor, applies light to a writing face rotated and moved to the rear side of the device, and converts into an electric signal by a CCD (Charge Coupled Device) line sensor, or the like; and a board surface fixed type that reads by moving a large-size image scanner closely on the surface of the whiteboard. Moreover, a read-data recording system is: a type that records on a paper sheet by thermal printing, ink-jet printing, electrophotographic printing, or the like; and a type that stores into a recording medium such as a Compact Flash™ memory.
Further, another example of a handwriting input device is a handwriting input device that converts a letter and a figure written and drawn on a display device such as a flat panel display by a pen-shaped instrument (a position indicator) into digital data (hereinafter, referred to as a display-type handwriting input device), and the input device is widely used as an input interface of a drawing instrument for graphics design and a digital whiteboard for a conference. A reading system is an electromagnetic induction type, an ultrasonic type, a pressure-sensitive type, etc., and all of the types detect the position coordinates of the pen-shaped instrument on the display device by various kinds of sensors (e.g., refer to Patent Document 1). The display-type handwriting input device changes the color of a pixel in the detected position coordinates on the display device, whereby a user can input a letter and a figure into a computer as if writing by a pen or a pencil on paper. Next, by executing computer processing such as an optical character recognition (OCR) process in real time on the inputted letter and figure, it is possible to display the inputted letter and figure written and drawn by hand on a display immediately after the letter and figure are inputted, which helps increase of the user's ability to express. Furthermore, it is also possible to use the inputted handwritten letter and figure as input parameters of the computer. For example, by interpreting the inputted figure as a boarder (e.g., a wing of an airplane) in fluid simulation and displaying an arrow representing the flow of fluid therearound together, it is possible to perform various kinds of design works as if sketching in consideration of the flow of the fluid occurring around the drawn figure. This is especially useful for outline design, which is the initial stage of design works.
Some of the display-type handwriting input devices, by using a plurality of position indicators having different identifiers or a position indicator that can change identifiers by a switch, can cause a computer to execute processes corresponding to the identifiers. For example, it is possible to realize an operation of inputting a letter and a figure by one position indicator and erasing the inputted letter and figure by another position indicator.
FIG. 24 is a block diagram showing an example of a display-type handwriting input device described in Patent Document 1. Loop coils C1 to C48 and C1′ to C48′ generate an electromagnetic field or convert a change of the electromagnetic field into electric current when alternating current is flown therethrough. An X-direction (Y-direction) selection circuit 221X (221Y) selects a loop coil to be used from among the plurality of loop coils. An X-direction (Y-direction) connection switching circuit 222X (222Y) exclusively connects the loop coil being used to a transmission circuit 223 or a reception circuit 224. The transmission circuit 223 and the reception circuit 224 generate and detect an alternating current signal of a given frequency, respectively. A processing device 225 executes control of the whole device and processing of the detected signal. A position indicator 226 incorporates a tuned circuit 227 that oscillates in tune with an electromagnetic field of a specific frequency. Then, a display device 228 displays information in accordance with the result of the processing of the detected signal.
An operation of this device will be described. Firstly, the transmission circuit 223 generates an alternating current of a frequency f1. This alternating current signal is sent out to one of the loop coils, for example, the loop coil C1 (C1′) via the X-direction (Y-direction) connection switching circuit 222X (222Y) and the X-direction (Y-direction) selection circuit 221X (221Y), and is converted into an electromagnetic field of the frequency f1 by the loop coil C1 (C1′). At this moment, when the position indicator 226 incorporating the tuned circuit 227 tuned to the frequency f1 is in the vicinity of the loop coil C1 (C1′), the tuned circuit 227 oscillates. After that, when a connection destination of the loop coil C1 (C1′) is changed from the transmission circuit 223 to the reception circuit 224 by the X-direction (Y-direction) connection switching circuit 222X (222Y), the electromagnetic field generated by the loop coil C1 (C1′) immediately disappears, but the oscillating tuned circuit 227 gradually discharges electricity. During this time, the position indicator 226 generates an electromagnetic field of the frequency f1. The electromagnetic field generated by the position indicator 226 is converted into an alternating current signal of the frequency f1 by the loop coil C1 (C1′), and detected by the reception circuit 224 via the X-direction (Y-direction) selection circuit 221 X (221 Y) and the X-direction (Y-direction) connection switching circuit 222X (222Y). Then, the reception circuit 224 transmits detection of the position indicator 226 in the position of the loop coil C1 (C1′) to the processing device 225. The processing device 225 repeatedly executes this operation while sequentially changing a loop coil to be used, thereby detecting the X-coordinate and Y-coordinate of the position indicator 226. Then, the display device 228 changes the color of a pixel in the detected position coordinates to a color different from the background color, and feeds back detection of the position indicator 226 in that position to the user.
Although not directly described in Patent Document 1, it is possible to realize the operation of inputting a letter and a figure by one position indicator and erasing the inputted letter and figure by another position indicator. For example, the transmission circuit 223 further generates an alternating current signal of a frequency 12 different from the frequency f1 subsequently. As a result, the position coordinates of another position indicator incorporating a tuned circuit that oscillates in tune with the frequency 12 are detected. The display device 228 changes the colors of pixels around the detected position coordinates of the position indicator tuned to the frequency 12 to the background color, whereby the user's operation of erasing the inputted letter and figure is realized. In the case of using a position indicator that can change a tuned circuit oscillating at a plurality of different frequencies by a switch, it is possible to detect the position coordinates of a single position indicator and the state of a change by the switch instead of the position coordinates of a plurality of different position indicators, so that the user can switch between a drawing mode or an erasing mode by the switch.
[Patent Document 1] Japanese Patent Publication No. 2139446
[Non-Patent Document 1] Z. Zhang, “A flexible new technique for camera calibration,” IEEE Transactions on Pattern Analysis and Machine Intelligence, Vol. 22, Issue 11, pp. 1330 to 1334, 2000
[Non-Patent Document 2] Richard Hartley, et al., “Multiple View Geometry in Computer Vision,” Cambridge University Press, pp. 32 to 37, 2000
The greatest merit of a handwriting input device is that a letter and a figure can be converted into digital data by an operation method that many users have already learned, which is writing a letter and drawing a figure by a pen-shaped instrument such as a marker on a working plane such as a whiteboard. In other words, use of a handwriting input device makes it possible to easily use various kinds of processing abilities of a computer without learning a method of operating an input device such as a keyboard and a mouse specialized for a computer.
However, in the case of an electronic-blackboard-type handwriting input device, it is impossible to recognize a letter or a figure written or drawn on a white sheet or a whiteboard in a dark place. Therefore, for example, when making a presentation in a dark room to show slides, it is difficult to use the electronic-blackboard-type handwriting input device.
On the other hand, because a display-type handwriting input device displays a written letter and a drawn figure on a display screen, not only it has no problem even in a dark atmosphere, but also it makes easy to visually recognize. However, unlike the electronic-blackboard-type handwriting input device that leaves a letter and a figure written and drawn by hand on a white sheet or a whiteboard, the display-type handwriting input device stores the inputted letter and figure only as digital data in a computer. Therefore, in case the stored digital data is lost, input information is completely lost. Moreover, while the electronic-blackboard-type handwriting input device allows an operation of erasing all or part of written letters and drawn figures without using a special instrument such as tissue paper and a fingertip, the display-type handwriting input device needs a special instrument (e.g., a dedicated position indicator).
Thus, the electronic-blackboard-type handwriting input device and the display-type handwriting input device each have a merit and a demerit.